1. Field of the Invention
The present invention relates to an envelope waveform generation apparatus which is applicable to electronic musical instruments and generates an envelope waveform in order to control the tone volume amplitude of musical tones.
2. Background Art
FIG. 10 shows the composition of an electronic musical instrument to which a conventional envelope waveform generation circuit 4 has been applied. In the diagram, reference numeral 1 indicates a keyboard comprising a plurality of keys; when one of the plurality of keys with which this keyboard 1 is provided is operated by depression, this is detected by key depression detection circuit 2. Key depression detection circuit 2 outputs a key code KC which corresponds to the depressed key and outputs a key-on signal KON during the period in which the key is being depressed; key code KC is supplied to musical tone signal generation circuit 3, and furthermore, key-on signal KON is supplied to envelope waveform generation circuit 4. Reference numeral 5 indicates a tone color selection apparatus, which is for the purpose of the selecting a desired tone color from among a plurality of piano or organ tone colors or the like. This tone color selection apparatus outputs a tone code TC corresponding to the selected tone color to envelope waveform generation circuit 4 and musical tone signal generation circuit 3. Envelope waveform generation circuit 4 generates, in response to the arrival of key-on signal KON, an envelope waveform ENV corresponding to tone code TC, and supplies envelope waveform data ENVD corresponding to this envelope waveform ENV to musical tone signal generation circuit 3. Envelope waveform ENV comprises for example, as shown in FIG. 11, the four segments known as attack part A, decay part D, sustain part S and release part R. At the point in time at which a key is depressed and key-on signal KON is received, attack part A begins, then delay D and sustain S are proceeded to, and at the point at which the key is no longer pressed (key-off) and the reception of the key-on signal KON is halted, release part R begins. Musical tone signal generation circuit 3 generates, in accordance with the envelope waveform data ENVD supplied by envelope waveform generation circuit 4, a musical tone signal with a tone color corresponding to the tone code TC supplied by tone color selection apparatus 5 at a tone pitch corresponding to the key code KC supplied by key depression detection circuit 2. The musical tone signal outputted from this musical tone signal generation circuit 3 is converted to an analog signal by D/A converter 6, then supplied to a sound system 7 comprising amps, speakers and the like, and emitted from this sound system 7 as a musical tone.
In this type of electronic musical apparatus touch response control, initial touch control and after-touch control are known; however, in conventionally known technology, the degree of effect with respect to any musical tone which is key-touched is dependent solely on the strength of the key touch, and the changing of the state of effect of the key touch in each segment was unknown.
The applicants have previously submitted an electronic musical instrument (Japanese Patent Application, 2nd publication, No. Hei 1-55469) which is provided with an initial touch detection mechanism which detects the initial key touch of a depressed key and outputs an initial touch detection signal, and an after-touch detection mechanism which detects key touch while a key is being depressed and outputs an after-touch detection signal. In this electronic musical instrument, the initial touch detection signal and the after-touch detection signal are combined in such a way that the proportion of the initial touch detection signal is large in the initial part of the envelope waveform, and the proportion of the after-touch detection signal becomes large after passing the initial part. In accordance with this type of electronic musical instrument, the initial touch component has a stronger effect in attack part A, and the after-touch component has a stronger effect once attack part A has been passed.
In general, an infinite variety of patterns of effect of touch are possible with respect to each segment from generation to termination of a musical tone, and an ability to change in various ways in accordance with the wishes of a performer or in accordance with a selected tone color is required. However, in the conventional electronic musical instrument described above, the effect of touch is predetermined to be a fixed pattern, so that this fixed touch effect pattern may in some cases generate disharmonies in musical tones with certain tone colors, and the freedom of the performer with respect to the touch effects in each segment is limited.